Aircraft control device



D `5 1944. B. G, cARLsoN i 2,364,128

' AIRCRAFT CONTROL DEVICE V v Flged April 22 1942 3 sl'leel'lS-Slleel'. 2

LEVA roR INVEN TOR..

' Arroelvcx Dec. 5, 1944.

B. G. cARLsoN AIRCRAFT CONTROL. DEVICE Filed `AprilV 22, 1942 5 Sheets-Sheet 5 A7' TOPNE )C Patented Dec. 5, 1944 AIRCRAFT CONTROL DEVICE Bert G. Carlson, Ericside, Ohio, assignor to Jack Heintz, Inc., Bedford, Ohio, a corporation of Application April 22, 1942. Serial No. 440,001

. 7 Claims.

This invention relates in general to automatic pilots for aircraft and more particularly to an automatic control for the amount and rate of elevator operation.

In the conventional hydraulic automatic pilot the gyro is air spun and its precession movements are transmitted through an air operated relay to the hydraulic system and to the aircraft control surfaces. One of the disadvantages of the conventional system, with respect more particularly to elevator control; is the tendency l of the automatic pilot toward over control as the aircraft pitches in normal straightaway flight. Another disadvantage is the difllculty encountered in automatic maintenance of a `desired flight-altitude.

An object of this invention is to provide a means whereby the amount of elevator applied will vary directly with the rate at which the aircraft pitches and to`provide a combined amount and rate follow-up system that will minimize or eliminate over controlling of the elevator and to reduce the cable loads as well as amount of pitch.

Another object is to provide a simple baromethorizon gyro is used to operate'an air relay, which in turn operates a balanced oil valve regulating the flow of pressure oil to the aileron servo cylinder. Interposed between this oil valve and the aileron servo is a spring balanced piston in each of the two oil pipe lines which are in cirl cuit with the hydraulic system as a whole.

rically responsive control system whereby a desired flight altitude may be manually set, obtained and maintained in spite of the usual tendency for the automatic pilot to correct for pitch by changing the fore and aft attitude which would interfere with the maintenance of a given flight altitude, all without over-control of the elevators due to sudden tendencies toward pitching.

According to the present invention there are provided two conventional air spun horizon gyros, one for bank control and one for pitch control, and one air spun directional gyro and airrelays to take charge of the elevator, aileron and rudder hydraulic servos for normal straightaway flight. Interjected into the hydraulic system is l an oil spun gyro with its own balanced oil valve. 'The oil spun gyro is sufficiently spring loaded so for normal straightaway flight it does not precess or interfere with the conventional ones operated by the air relay diaphragms. However, for purposes of controlling the amount and rate of a turn, when the oil is shut off from the air relay operated balanced oil valves, the balanced oil valve of the oil spun gyro regulates flow of oil to the servo motors and consequently takes charge of the operation of the rudder and aileron to the exclusion of the balanced oil valves that are operated by the air relays.

For the operation of the ailerons an air spun In straightaway flight the damped pendulum ofthe horizon gyro compensates for any gyro precession caused by acceleration which would apply aileron and put a` wing down. In turns this pendulum applies aileron to speed the recovery from violent yaws. In automatic turns it applies aileron simultaneously with or slightly in advance of, rudder application and the amount of aileron applied varies with the rudder load and the correct angle of bank.

Insofar as that part of the automatic pilot that automatically controlstheoperationof the elevators is concerned, the same air spun horizon gyro that controls the ailerons may be used. However, in the present invention a separate gyro is used for the elevator. In other words, one horizon gyro, or one that spins on a vertical axis may be used for aileron control andthe airpickoff so arranged as to compensate for precession in response to banking. An additional air spun vertical axis air spun horizon gyro is used for elevator control and provided with a-ir pick-offs so arranged as to compensate for precession in response to pitch. In addition to the conventional air relay and balanced oil valvefor operation of the elevator servo motor, there is also an added balanced oil valve in the hydraulic system that is under the control of, and regulated by, a barometrically responsive bellows that is calibrated and manually adjustable for desired flight altitudes.

The manual control system for the automatic pilot comprises ve control knobs, one of which centralizes the gyro -indicators before engaging the automatic pilot, one of which controls the operation of the conventional part of the automatic pilot for the rudder and aileron directional and horizon gyros, one of which is used. to change altitude with its dial calibrated in feet altitude, one of which shuts oiI and on the ow of oil supply to the main balanced voil valve .in the hydraulic circuitl and one which regulates the rate of turn through the oil spun gyro and its associated balanced oil valve to the rudder and aileron servo motors. 1

With the foregoingand other objects in view, the invention consists in the combination of parts and in the details of construction hereinafter set forth in the following specification and appended claims, certain embodiments thereof being illustrated in the accompanying drawings, in which: Figure 1 is a schematic view of the control system as applied to the aircraft control surfaces; Figure 2 is a schematic view of the control system showing certain parts for elevators,

ailerons and rudder control in transverse section;

Figure 3 is a view in longitudinal section taken through the barometrically responsive -automatic altitude control' for the elevators;

Figure 4 is a view in longitudinal section taken at right angles to Figure 3; and

Figure 5 is a view in elevation of the bar metric elevator control with a portion of the cover plate removed.

Referring more particularly to the drawings, Figure l'shows the conventional arrangement of aircraft ailerons i, elevators 2 and rudder 3 as well as the manual wheel control 4 and associated cables for operating the ailerons .and elevators and the conventionalrudder pedals 5 and associated cables for operating the rudder.

' As stated before, the present invention is more particularly directed to improvements in amoimt and rate oi.' rudder control and corresponding aileron control for stability and automatic turns and. as far as structure is concerned, itv mainly comprises the addition into an air relay controlled hydraulic system for rudder and aileron control of an oil spun gyro for controlling a balanced oil valve regulating flow of pressure oil to the rudder servo cylinder and a rudder as- .siston or oil pressure member, for regulating operation of the aileron servo in accordance with rudder operation in addition to the conventional air relay controlled balanced oilvalves regulating iiow of oil to .the rudder and aileron servo i Wunder.

Asshowninligure2,the oilspungyroassembly includes a casing I and a directional type o! gyro rotor 1 mounted on horizontal pivots l in a gimbal l toform a spinning axis correspondspring loaded biasing of the gimbal and its rotor,

for leading air under pressure through tube 40 or 4l to the air relay 42 on either -side of the diaphragm 43 for the actuation of the balanced oil valve 44, 45, 46 in casing 41 for regulating ilow of pressure oil through pipe 48 or 49 to the hydraulic servo cylinder 24 to either side of the .piston 25. for operating the rudder 3 through the piston rod 50 in either direction.

The air spun horizon gyro assembly in casing 5I includes a damped pendulum 52 for compensating for 'precession of the gyro by reason of acceleration. As is conventional, the air tubes 53 and 54 lead to an air relay- 55 to either side of a diaphragm 56 connected to a piston rod 5l lfor operating pistons 58, 59 and Gn of thebalanced oil valve in casing il. Also the pistons in this balanced oil valve regulate the ilow of pressure oil through pipes B2 and 63 to the aileron servo cylinder I4 to operate the aileron I in either direction through piston rod 66.

Arranged between pipes do anaal and pipes C2 and 63 is a rudder assister in a casing 61 with pipes 68 andls leading to pipes 2l and 2l and with pipes 10 and 1I leading to pipes 62 and,

'I'he rudder assister is actually for operating the ailerons and comprises a cylinder to receive a piston I2 spring pressed to the right by a comy pressioncoilspring 13 and to theflei't by a com.

ing normally to the longitudinal axis of the air- -u craft. The gimbal 9 is provided with trunnionsv Il and Il for rotation in suitable bearings in the casing. An oil Jet I2 discharges oil under pressure to gyro wheel buckets I3 to soin the wheel.

through the passageway I5 to the oil jet I2 and through passageway Il to 'cylinder I1. The passageways Il and I9 leading to pipes 2n and 2| are openedand closed by pistons 22 and 23. 'I'he 4side o! the piston 25 causes oil to be forced out of the cylinder on the .other side of the piston and out through the corresponding other pipe and f An oil simply pipe I '4 leads into the casing and pression coil spring 12' so as to be balanced. As shown the cylinder in which a corresponding piston 14 is located and balanced by springs 15 and 16, is in communication with pipes 69 and 1 I.

When itis desired to make an ordinary turn with the conventional part of the automatic pilot, without using the oil spun gyro assembly and without regard to predetermining the rate of turn, the knob 11 is left in the "oiT position leaving the oil stop valve 18 'open for distribution of pressure oil to the balanced oil valve in casing 41.

Turning of knob 19 through conventional gearing -as shown in Fig-ure 2, biases the air spun direcfurnishing of oil under pressure through pipe 20 causes a movement of the rudder 3in the c orresponding direction. In the position shown in Figure 2 both passages I8 and I9 are closed by pistons 22 and 2l.

Operation of the rate knob 2B. through appropriete shafting represented in dot and dash line 21 effects a rotation of shaft 28 and its worm 29 engaging a worm wheel 30 carried by a shaft Il mounted in suitable bearings in casing 6. Shaft II carries a segmental plate 32 iixed thereto which is provided with -appropriate recesses to be engaged by a fixed spring detent 33 so as to resiliently maintain the plate in various adjusted positions. The plate 3,2 has iixed thereto an arm 34 to receive one end of a tension coil spring 3l whose other end is secured to a pin 36 of a crank 31 keyed to the -gimbal trunnion II. .Thus an adjustment of control knob 26 effects a tional gyro assembly inrcasing 39 and the horizon gyroA assembly for operation of the rudder and ailerons'.

It willl be seen, that y despite the previously described spring loading of the oil spun gyro in the casing 6, if an abnormal yaw occurs and if there is any'tendency `toward overcontrol by the rudder, the oil spun gyro assembly will temporarily overcome its spring loading and take charge to eliminate such over control.- In this manner the amount of rudder applied varies directly with the rate at which the aircraft yaws oil course and the combined amount and rate follow-up eliminates over control. The damped pendulum l.'52 compensates for any precession of the horizon gyro caused by acceleration which would apply aileron and put a wing down. In turns this pendulum applies ailerons to maintain the correct amount of bank. v

In operation for autom tic turns the control knob |34 is turned to centralize-the gyro indicaltors before engaging the automatic pilot. The

control knob 11 is then turned toV on" position which through the oil stop valve 18 shuts oi! the supply of oil to the main balanced oil valves in easings 41 and 6|. The control knob 19 is then rotated untilthe top compass card 8| indicates in calibrated degrees the heading of the new course to be ilown. The control knob 26 is then turned, to the left orV right as required,` to index 30 denoting the rate of turn desired. As previously explained the turning of knob 26, through shafting 21, 28 puts the oil spun gyro 1 under flexible bias through spring 35 and consequently the balanced oil valve 22, 23 regulates the flow of oil to either side of the piston 25 in the rudder servo cylinder 24. The turn thus initiated will continue until the off-on control knob 11 is turned to off position and the .rate" control knob 26 is turned to zero position. In other words, the fixed rate of turn will continue as long as called for. Knob 11 should be turned to oif" position and knob 26 should bereturned to Zero position within 30 degres, plus or minus spread of the two compass cards 8| and ,82 in order to straighten out on the compass heading set for to 15 degrees in advance on approaching a course originally set to avoid over run. If this spread has been exceeded the control 'knob 26 should be turned hard over, in the corresponding direction, and returned to zero position when the compass cards 8| and 82 approach alignment within the 60 degree spread.

As the pressure oil from pipes 20 and 2| deliver oil undergreater pressure either to the left or right of piston 25 in the rudder servo cylinder 24 to apply left or right rudder a corresponding greater oil pressure is applied through pipe 69 or 68 to piston 14 in the rudder asslstor. Should the oil pressure in. pipe 69 be greater than that in pipe 68, the pressure of the column of oil on valve 12 plus the expansive forceof spring 12 overcomes the balancing action of compression spring 13 and thus valve 12 is forced from right -ing aileron control slightly precedes the initiation and completion of the rudder control for such automatic turns s6 as to insure proper bank and turn and eliminate any tendency for the aircraft to skid. It, of course, follows that control of the rudder in the opposite direction brings piston 14 of the rudder asslstor into action to correspondingly effect an appropriate aileron control.

For purposes ofelevator controlby the automatic pilot a separate horizon gyro may be em- 'ployed and soprovided with air pick Voils that it will function only as a climb gyro. Such a gyro is shown at 83 enclosed in a casing 84 with tubes 85 and 86 leading from the air pick ofi' to the air relay 81 on either side of the diaphragm 88 which through its connection through piston rod 89 operates the balanced oil valves 80, 9| and 92 in the'casing 93. The pressure oil from the bal-Y anced oil valve Ain casing 93 'leads through tubes 94 and 95 to the elevator servo cylinder 86 on eitherside of servo piston 91 which is connected the same in the corresponding direction.

' and |0|` leading to either side of. servo piston 81. The supply of oil for hollow vane |03 in casing 83 comes from'the oil pump through tube |02, casing 83 being provided with a drain outlet and tube |38 leading to the oil sump. Vane |03 is provided with a hollow axis |04 which registers with pipe |02 and the vane and its hollow :interior taper upwardly to its upper end to form a nozzle |05. Vane |03 is counterweighted by an adjustv able counterweight |22. Above and adjacent to the nozzle-is a bracket |06 divided into two upwardlywidening passages |01 and |08 with a tapering knife edge partition |08 lbetween the same.; These passages communicate with passages 0l 4tube |89 to the sump. `The oil for operatingservo piston comes fromtubes |02b and |02a into either tube |00 or |0|. The servohousing 98 is provided with two outlet tubes |40 and |4| com municating with tube |39 leading to the sump t so that when oil goes to one of tubes |00 or |0| it is allowed to escape through the other r through outlets |40 or |4| to drain pipe |39 to the sump. i

Also installed within the casing 99 is a barometrically responsive bellows ||5 secured at ||6 to the casing. Through the medium of a toggle joint including pivotally connected links ||1, ||8 and H9 the bellows bracket |20 is f connected pivotally at |2| to pivoted vane |03 below its piv-v otal axis |04. Thus as the bellows expands or contracts in response to variations in barometric pressuresthis movement of the bellows is trans.- lated through thetoggle mechanism to the vane |03 which is rotated about its pivot accordingly. As long as the vane and its nozzle |05 is in neutral position as shown in Figure 3and on dead center with respect to the knife edge partition |09 an equal amount of pressure oil is distributed to either end of cylinder ||2 and the oil valve assembly is balanced and no pressure is added through pipes |00 or |0| to the elevator servo cylinder. When, however, thebellows contracts or' expands andthe vane nozzle is moved to the left or right, an unequal pressure resulting unbalances the oil valve causing the servo piston to move to the left or right and depress orI elevate the elevators to cause a shift of attitude of the In order to regulate the amount and rate oi' elevator control there is provided an additional balanced oil valve in casing 88 with pipes |00 aircraft to ascending or descending position.

|23 and une H1 of the toggle. i This arm |23 has I connected thereto a tensin coil springl |25 which is also connected to a casing bracket |26. Extending through the casing in a suitable bearing sleeve |21 is a shaft |28 that carries a worm gear |28 meshing with a worm wheel |30 carried by a shaft |8|. This shaft |3| also has fixed thereto a. cam |32 that bears against arm |23. The shaft |3| extends to a knob |33 for manual setting of the nozzle |054 with respect to the passages y|01 and |08 of the hydraulic valve assembly. l

In operation the knob |34 is used to centralize the gyro indicators before engaging the automatic pilot. The control knob |33 is used to change altitude in that an adjustment of the vane nozzle |05 to the left or right of dead cen- 4 ter position will vary the pressure in either end.l

of the hydraulic valve assembly and cause the elevator to change the 'attitude of the aircraft either upwardly `or downwardly aboutl its` trans'- verse axis. When the desired altitude has b 'een reached the expansion or contraction of the' barometric bellows existing at the manually 'set' altitude opergttea the toggle to lbring the vane nozzle once again in dead center position to balance the hydraulic va1ve.. In straight night and in turns the Vbarometric pressure controls the hydraulic valve which operates to attain and maintain the desired altitude. This is also-true when the conventional lpart of the automatic has .been provided an automatic pilot system wherein the amount of rudder applied will vary directly `with the rate at which' the aircraft yaws off course and wherein the combined amount and rate follow-up will eliminate over control.

It will also be seen that there has been provided an aileron control, in the form of a rudder horizon gyro compensates for any gyro precession caused by acceleration which would apply aileron. In turns this pendulum applies aileron to maintain the correct amount of bank. The rudder assistor applies aileron to speed recovery from violent yaws and in automatic turns it applies aileron simultaneously with, or slightly prior to, rudder application and the amount, of aileron applied varies with the rudder load and the cQrrect angle of bank.

The oil `spfun gyro assembly and balanced oil valve and rudder assistor, or aileron control, controlled thereby under control of the ra knob effectively brings about a controlled operation of rudder and ailerons together and a consequent controlled rate of turn and may be readily installed as a unit in the hydraulic system of any conventional hydraulic automatic pilot.

The automatic barometric amount and rate of elevator control makes it easily possible to attain and vmaintain a desired night altitude despite tendencies of the aircraft lto pitch as a result of gusts and airpockets. and shifts of center of gravity which might tend toward overcon-y piston` operated elevator servo motor for maintaining the proper aircraft attitude in elevation, ofv supplemental means for maintaining level night `and predetermining and regulating aircraft ascent and descent, said means including a supplemental pressure oil line in said hydraulic system leading to said servo motor, a. balanced oil 'valve in said line, a barometric means, a control device `operated thereby for operating said valve and said yservo motor in either direction and alternate manual means for operating said barometric means and said' servo motor ln either direction, said control device comprising a pivoted nozzle in said pressure oil linel arranged when in neutral position to deliver equal pressure oil to both ends of said last-named oil valve to balance the same', said nozzle being connected to I said barometric means so as to beautomatically operated thereby in response to barometric conditions so as to maintain night level attitudes.

sive hydraulic system having a balanced oil valve and piston operated elevator servoy motor for'vmaintaining the proper aircraft attitude in elevation, of supplemental means for maintaining level night and predetermining and regulat ling aircraft ascent and descent. said means in-lcluding a. vsupplemental pressure oil line in said comprising a pivoted nozzle in said pressure oil line arranged when in 'neutral position to deliverequal pressure oil to both ends of said lastnamed oil valve to balance the sama-said nozzle being connected 'to said barometric means so as assister, in which a damped pendulum for the to be automatically operated thereby in response to barometric conditions so as to maintain night level .,attitudes, said alternate manual control means being adapted to bias said nome to one side or the other away from neutral to predeterminedly set andl attain a given night altitude either by ascent or descent.

3. In an automatic pilot for aircraft, the combination with a gyroscopic precession responsive hydraulic system having a balanced oil valve and piston operated elevator servo motor for maintaining the proper aircraft attitude in elevation,

of supplemental means for maintaining level night and predetermining and regulating` aircraft ascent 'and descent, said supplemental means including a supplemental pressure oil line in said hydraulic system, oil lines leading to either side of said servo piston, a balanced oil valve iny said oil line for controlling the delivery of pressure oil to said servo motor oil lines to operate s'aid servo piston in either direction, inlet passages for delivering pressure oil to either side o! said last-named balanced oil valve, a pivoted hollow vane in said oil line and adapted when in neutral position for delivering equalized pressure oil to said inlet passages, a barometric responsive device connected to said vane for controlling the relation of its outlet with respect to said neutral position, and to create a differential in pressure withinsaid last-named'balanced oil valve when deviated from said neutral position in either direction.

' 4. In an automatic pilot for aircraft, the com.

bination with a gyroseopic precession responsive hydraulic system having a balanced oil valve and piston operated elevator servo motor for maintaining the proper aircraft attitude in elevation,

of supplemental means for maintaining level night and predetermining and regulating air' craft ascent and descent, said supplemental means including a supplemental pressure oil line in said hydraulic system, oil leads to either side named balanced oil valve, stationary means for equally dividing said inlet-passages, a pivoted hollow vane in said oil line for delivering pressure oil to said inlet passages. a barometric responequal quantities of pressure oil to both of said inlets whenin neutral position with respect to said dividing means, and to create a diderential in pressure within said lastnamed-balanced oil valve when deviated from said neutral position in either direction.

5. In an automatic pilot for aircraft, the combination with a gyroscopic precession'responsive hydraulic system having a balanced oil valve and piston operated elevator servo motor for maintaining the proper aircraft attitude in elevation, of supplemental means for maintaining level iiight and predetermining and regulating aircraft ascent and descent, said supplemental means including a supplemental pressure oil line in said hydraulic system, oil lines leading to either side of said servo piston, a balanced oil valve in said oil line for controlling the delivery of pressure oil to said servo motor oil lines to operate said servo piston in either' direction, inlet passages for delivering pressure oil to either side of said lastnamed balanced oil valve, a knife edge partition for dividing the passage of oil into said inlet passages, a pivoted hollow vane in said oil line for delivering pressure oil to said inlet passages, a

, barometric responsive device connected to said vane for controlling the relation of its outlet with respect to said partition so as to deliver equal quantities of pressure oil to both of said inlets when in neutral position with respect to said partition, and to create a differential in pressure within said' last-named balanced oil valve when deviatedfrom `said neutral position in either direction. 1

6. In an automatic pilot for aircraft, the combination with a gyroscopic precession responsive hydraulic system having a balanced oil valve and piston operated elevator servo motor for maintaining the proper aircraft attitude in elevation,

oil line for controlling the delivery of pressure oil to said servo motor oil lines to operate said servo piston in either direction, inlet passages for deof supplemental means for maintaining level i'light and predetermining and regulating aircraft ascent and descent, said supplemental means including a supplemental pressure oil line in said hydraulic system. oil lines leading to either side of said servo piston. a balanced oil valve in said livering pressure oil to either side of' said lastnamed balanced oil valve, a pivoted hollow vane in said oil line and adapted when in neutral position for delivering'equalized pressure oil to said.

inlet passages, a-barometric responsive device connectedto said vane for controlling the relation of its outlet with respect to said neutral position, and to create a differential in pressure within said last-named balanced oil valve when deviated from said neutral position in either direction and alternate manual means for operating said baro'- metric means and said servo motor in either direction.

7. vIn an automatic pilot for aircraft, the combination with a gyroscopic precession responsive hydraulic system having a balanced oil. valve and piston operated elevator servomotor for maintaining tlie proper aircraft attitude in elevation, of supplemental rmeans for maintaining level flight and predetermining and regulating aircraft ascent 'and descent, said supplemental means including a supplemental pressure oil line in said hydraulic system, oil lines leading to either side of said servo piston, a balanced oil valve in said oil line for controlling the delivery of pressure oil to said servo motor oil lines to operate said servo piston in either direction, inlet lpassages for delivering pressure oil to either side of said lastnamed balanced oil valve, a knife edge partition for dividing the passage of oil into said inlet pas-4 when in neutral position with respect to said partition, and to create a differential in. pressure within said last-named balanced oil valve when deviated from said neutral position in either di`- rection and alternate manual meansfor operating said barometric means and said servo motor in either direction.

- BERT G. CARLSON. 

